The technical field generally relates to engine aftertreatment control systems. Previously known engine aftertreatment control systems include selective catalytic reduction (SCR) systems that divide the SCR catalyst portions into more than one catalyst element, and determine a NOx or NH3 value between SCR catalyst portions. Previously known engine aftertreatment control systems control the NOx value between SCR catalyst portions to a minimum possible value, and/or control the NH3 value to a selected NH3 concentration. However, such engine aftertreatment control systems suffer from various limitations, including at least that such systems cannot control the NH3 to NOx ratio between SCR catalyst portions to a selectable level, and/or control the NOx amount between SCR catalyst portions to a selectable level. Accordingly, further technological developments are desirable in this area.